A method and a device for the fabrication of concrete blocks, in particular paving stones, is known, for example, by means of European Patent Application 0 319 972. In accordance with this European Patent Application, however, concrete blocks having special surface structure are fabricated, but not concrete blocks having through holes.
It is therefore an object of the present invention to modify known methods and devices in such fashion that concrete blocks, in particular paving stones, of various formats and sizes having thin through holes for water drainage (perforated blocks) can be fabricated. It is intended that both concrete blocks having smooth surface and those having rough or roughened surface can be fabricated. This object of the invention is achieved by virtue of the fact that core pins are arranged in the region of the male dies or of the mold table or on the mold; that the core pins are introduced at least partially inside the mold before the compaction of the concrete; that the concrete is then compacted by means of an advance of the male die; that the core pins or the compacted concrete blocks are then at least partially removed from the region of the mold or of the core pins, and afterward the male dies and, to the extent that this has not already happened, the core pins are retracted from the region of the compacted concrete blocks or the compacted concrete blocks are raised out of the region of the core pins and the concrete blocks are completely removed from the mold.
The core pins may be mounted directly or indirectly on the male die whereby they are advanced and retracted with said male die, so that the core pins initially penetrate into the still-uncompacted soft concrete and, indeed, penetrate farther and farther until the male die comes into contact with the upper face of the still-soft concrete and compacts the same, said pins extending to the mold table, so that by this means thin through holes are molded into the compacted concrete blocks. Afterward, the mold is preferably raised first, then the male dies with the pins, so that complete molded concrete blocks are present. So that the pins can be withdrawn from the still-soft, uncured concrete block without damaging the same, it is advantageous if the pins are designed in conical form.
There also exists, however, the possibility that the core pins are mounted not on the male die or a die plate but on the mold. This can be accomplished, for example, via at least one web that is mounted on the mold and to which the core pins in turn are attached by one end. They then project into the mold and, indeed, as far as the mold table. In this case, the concrete is charged into this so-designed mold and then compacted with a male die that, in correspondence with the number of webs, consists of a plurality of end faces adapted to the webs. The mold is then raised, and afterward the male die, so that the desired concrete blocks having thin holes are again present.
Finally, there also exists another possibility that the core pins are mounted on the mold table and their free ends point in the direction of the male die or die plate. In this case, the length of the core pins can be adjusted so that they, in combination with the quantity of concrete charged, just come into contact with said concrete after compaction by means of the male die. Openings or recesses can, however, also be made in the male die so that the core pins in the final compacted condition extend into said openings or recesses. If the core pins are mounted on the mold table, then for demolding the mold is preferably raised simultaneously together with male dies or die plate, the still-soft compacted concrete blocks being assumed to be lifted along with said mold, so that they are raised from the mold table and the core pins. Afterward, after removal of the mold table with the core pins, or by means of setting down next to the mold table, the concrete blocks are pressed out of the mold in usual fashion, and indeed by means of raising the mold or depressing the male die. Also in this case it is advantageous if the core pins are designed in conical form. The molds can also be designed in slightly conical form, that is, narrowing slightly toward the mold table, so that the still-soft concrete blocks better adhere in the mold and are raised along with the same.
In development of the invention, it is proposed that a movable component having core pins is arranged in the region of the male dies or of the mold table; that the core pins are introduced at least partially into the concrete inside the mold before the compaction of the concrete; that the concrete is next compacted by means of an advance of the male dies; that the core pins are then retracted at least partially out of the region of the mold and the male dies and, to the extent that this has not yet happened, the core pins are afterward retracted out of the region of the concrete blocks and the concrete blocks are demolded. The expression "at least partially" in connection with the movement of the core pins both into the concrete-filled mold and out of the mold was selected because, depending on the development of the device, it is possible in accordance with the invention either to move the core pins independently of the male die in such fashion that the core pins are completely introduced into the concrete and the concrete is then compacted by means of the male die, and that the core pins are then again completely removed from the region of the mold, the male die afterward being retracted or raised and the concrete blocks demolded. It is also, however, possible in accordance with the invention to couple the movement of the core pins and the movement of the male die together, at least intermittently or partially, in such fashion that the core pins initially are pushed only a certain depth into the concrete inside the mold and are then advanced together with the male die, and conversely initially lifted out of the compacted concrete only to the extent that a raising together with the male die is possible without damage to the still-soft compacted concrete blocks. The last procedure is, in particular, possible without problems if the core pins are designed in conical form.
In development of the method, the component on which the core pins are mounted is advantageously supported and guided outside the male die. The core pins are introduced into the concrete through openings in the male die as far as the mold table.
The method can, however, also be performed in such fashion that the component is supported and guided on the mold table and that the core pins are introduced into the concrete through openings in the mold table as far as the male die. Supported and guided on the mold table means that the component can be both arranged in a larger-volume mold table and also supported beneath the mold table.
In the case of a device for the performance of the method for the fabrication of concrete blocks having thin through holes for water drainage (perforated blocks), it is proposed that core pins are arranged in the region of the male dies or of the mold table or of the mold, which core pins are arranged inside the compaction space at least during the compaction of the concrete by means of the male dies. These are the basic forms of the device by means of which, with slight modifications, concrete blocks having thin holes can be fabricated on known devices. Depending on the design, the core pins, because mounted on the male dies, are inserted into the soft concrete and again withdrawn therefrom simultaneously with the raising and lowering of the male dies, or said core pins, by virtue of arrangement on the mold or on the mold table, are located in the cavity before the concrete is charged and are withdrawn after compaction of the concrete blocks.
In further development of the device, it is proposed that the male dies exhibit openings; that core pins are arranged preferably on the center line of the openings, which core pins are mounted on at least one component; that the component is arranged on the side of the male die opposite to the mold and is at least partially displaceable in the direction of motion of the male die, independently of said male die; and that the displacement path of the component is designed such that the ends of the core pins, on the one hand, extend to the mold table in the advanced position of the male die and, on the other hand, extend to above the surface of the concrete in the retracted position of the male die. The movement of the component having the core pins can be both dependent on and independent of the male die, for example can be effected by means of hydraulics or pneumatic cylinders or mechanically/electrically by means of electrically actuated spindles. In the case of a solution in which the component having the core pins is moved in completely independent fashion, one or a plurality of adjusting devices can engage a machine frame independently of the male die and its connecting rod. The adjusting device or devices can, however, also engage the male die or a component connected to the male die. The adjusting device can also be designed to operate in simple fashion and can be in effective connection with springs that exert opposing forces.
A simple solution also consists in that the components supporting the core pins are mounted on a connecting rod or connecting pipe or, depending on size, can also be mounted on a plurality of connecting rods and connecting pipes of the machine. The connecting rods or connecting pipes are the structural elements that ordinarily raise and lower the male die or male dies or die plate and compact the concrete. The component or components that support the core pins can advantageously be rigidly mounted on these connecting rods and the male dies for compaction can be elastically supported, inside stops, against these connecting rods. In this case, the core pins therefore initially penetrate at least partially into the concrete until the male die is in contact with the concrete, and then penetrate further as far as the mold table, the male die then yielding in elastic fashion and accomplishing a complete compaction of the concrete only at the end, via the stop. In the reverse motion, the core pins are raised first, the male die or male dies still exerting a residual pressure on the concrete block via the springs, the core pins and the male dies afterward being raised until they are supported above the surface of the concrete blocks and the latter can be removed.
Because the mold is also advantageously raised for the demolding of the concrete blocks, the mold or the component having the core pins can exhibit lugs or projections by means of which the mold is raised at least partway when said component is raised. This can advantageously happen on such a partial path or at such a time that the male dies are still exerting a residual pressure on the concrete blocks, so that the shear force between the mold and the soft concrete block is overcome.
So that grooves can be molded into the bottom of the molded blocks in combination with the holes, the mold table or a drawing sheet arranged on the mold table exhibits strips that exhibit a half-round, cornered, or knife-edge-shaped external contour, corresponding to the desired groove. The strips exhibit openings or longitudinal slots, which are adapted to the core pins or the cross sections of the core pins, so that the latter can extend into said strips. By this means, the core pins have a free space in which they attain, at various heights, such a final position that the male die or male dies can compact the concrete uniformly and without hindrance. This is significant because it cannot be insured that the quantity and density of concrete charged into the mole is always the same. Preferably, the strips are designed hollow and the drawing sheet or the mold table exhibits openings that are in effective connection with the voids. By this means, concrete particles pressed by the core pins into the voids of the strips can again escape.
Because, depending on the design of the molding machine, the drawing sheet is pulled out from under the concrete blocks before said concrete blocks are demolded, so that the concrete blocks come to lie on the mold table or a board, it is advantageous if the longitudinal axes of the strips are oriented parallel to the direction of motion of the drawing sheet, so that the latter can be pulled out from under the concrete blocks without further preparations. If longitudinal slots are arranged in the strips, then the core pins can initially remain in the compacted, still-soft concrete blocks until the strips have been pulled out from under the concrete blocks. By this means, the holes are not clogged or closed by means of the movement of the strips.
As already stated in connection with the method, the device for the performance of the method can also be designed such that the mold table exhibit openings; that core pins are arranged preferably on the center line of the openings, which core pins are mounted on at least one component; that the component is arranged on or in the mold table on the side opposite the mold and is displaceable toward and away from the male die; and that the displacement path of the component is designed such that the end of the core pins, on the one hand, extend to the male die in its lowered position and, on the other hand, extend into openings inside the external surface of the mold table facing the mold or the strips arranged on the mold table or drawing sheet to above the surface of the concrete in the retracted position of the male die. The male dies can also exhibit openings, and the displacement path of the components can be designed such that the ends of the core pins extent into the latter. For the acceptance of the component or components, the mold table or the drawing sheet can be designed in double-wall fashion, and the component can accommodate adjustment devices, springs, and the like. The adjustment devices and/or springs can, however, also be supported outside the mold table or the drawing sheet. In the device last describes, the charging and compaction of the concrete blocks takes place in the known fashion and with the known male dies, while the fabrication of the holes in the concrete blocks takes place by means of core pins, which are inserted from the mold table after the charging of the molds with concrete. In the case of the embodiment having core pins in the region of the mold table, however, the core pins can also by introduced into the mold already before the mold is charged with concrete, the charging and compaction then taking place afterward.
How the method is performed and how the device is designed, that is, whether the core pins are mounted on the male die, on the mold or the mold table, or whether the core pins are introduced into the concrete from the side of the male die or from the mold table, depends on how this can be most simply designed from case to case and what preferences are assigned greatest weight.
It should further be pointed out that the cross section of the core pins can be arbitrary. Initially, it is thought to design said cross section round. It can, however, also be designed oval or square or rectangular. A cross shape having narrow webs can also be advantageous. How the cross section of the core pins is designed is less a question of the fabrication method or of the design of the device than a question of how the cross section of the openings in the perforated blocks should be in the finished condition and what quantities of water are to be drained away.